1. Field of Invention
This invention relates in general to dam arrangements for controlling water flow. More particularly, the invention relates to dam arrangements of the type that include an inflatable and collapsible member, such as, for example, a flexible membrane. Even more specifically, the invention is directed to the control chamber arrangement for controlling the inflating and collapsing of the flexible membrane.
2. Description of The Prior or Related Art
Conventional inflatable and collapsible dams utilize a flexible membrane member formed as an envelope or bag to serve as the weir of the dam. This flexible membrane is generally coated with rubber at least over those portions of the membrane that would be in contact with the water. To inflate the flexible member, a pressure medium such as, for example, air and/or water is pumped into the interior of the member. Sufficient pressure is built up in the envelope to make it self supporting.
To collapse the membrane bag, the pressure medium is discharged from the interior of the flexible member and it contracts. As an example of a conventional inflatable and collapsible dam of this type, see Japanese Patent Publications Nos. 11702/65 and 2371/69.
Conventional inflatable and collapsible dams of the flexible membrane type include a control chamber positioned generally as shown in either FIGS. 1(A) and 1(B) or as shown in FIGS. 2(A) and 2(B) (all prior art). As shown in these figures, a conventional control chamber 50 includes an upper section which projects above the ground and a lower section that is buried underground. The upper and lower sections together constitute a single unit into which all control mechanisms for operating the dam are incorporated.
In FIG. 1(A) (prior art), there is a weir 24. Conventional control chamber 50 is installed on an embankment 22 of a river. Also shown in FIG. 1A are an upper stream water level sensing pipeline 8 and a feed and exhaust pipeline 10. More of the details of conventional control chamber 50 are shown in FIG. 1(B) (prior art).
Referring to FIG. 1(B) (prior art), there is shown a more detailed diagram of one embodiment of a conventional control chamber 50 of the type used in the FIG. 1(A) construction. Chamber 50 includes an automatic inflater means including a float 51 for sensing water level. Float 51 is responsive to an automatic collapse water level 36. The lower section of the control chamber 50 is positioned at an elevation that is lower than a level at which automatic collapse is effected. A blower 1 draws air into the system through an air filter 54 and forces it into an air delivery pipe 55. Air pressure is indicated by a pressure gauge 56. Forced air flows through a valve 57 and a feed and exhaust pipeline 10 to weir 24. Float 51 actuates a pressure relief valve when the dammed water level reaches an automatic collapse water level 36. Upper stream water level sensing pipe 8 provides a water flow to the chamber 50 in which float 51 is positioned.
FIG. 2(A)(PRIOR ART) shows an alternative conventional dam arrangement. In this arrangement, the lower portion of control chamber 50 is lower in elevation than the lower portion of chamber 50 in the FIG. 1A arrangement.
Referring now to FIG. 2(B), there are shown the construction details of chamber 50 of the FIG. 2(A) (PRIOR ART) embodiment.
A water seal pipe 4 provides an indicator of river water level so as to permit automatic collapse at level 36, an inner pressure sensing pipe 53 and a pressure gauge 3 which displays weir pressure. The conventional arrangements may also include a filter 54 for filtering air blown into the system by blower 1, and an air delivery pipe 55. Control chamber 50 also includes a valve 57, pulley 58, and an automatic flattener means relying on a reservoir bucket 6 (rather than on a float 51 shown in FIG. 1(B)) which is positioned at an elevation that is lower than a level at which a base of weir 24 is positioned. This arrangement permits automatic discharging and draining of weir 24 by feed and exhaust pipeline 10 during flattening or collapsing of the weir 24. There are also a bypass valve 59 and an exhaust valve 160. Water level 52 is at the top of weir 24.
The alternate known control mechanism shown in FIGS. 1(B) and 2(B) (PRIOR ART) are more completely described in Japanese early publication no. (OPI) 79928/79 corresponding to British Patent No. 1,602,335.
To fabricate the collapsible dam as shown in FIGS. 1(A) and 1(B) (prior art), it is necessary to dig or excavate the embankment 22 of the river being dammed at least to a level at which automatic flattening of the weir 24 occurs when the weir 24 and control chamber 50 are piped so that the upper stream water level sensing pipeline 8 is positioned at a level less than that at which automatic flattening of the weir 24 is established. To fabricate the dam as shown in FIGS. 2(A) and 2(B), it is necessary to dig the continuation of the weir 24 and the control chamber 50 to a level of the riverbed for horizontally conducting feed and exhaust pipeline 10 to control chamber 50 under the river bed. If conventional control chamber 50 is positioned in the interior of the embankment 22, it is necessary to dig into the embankment 22 for placing the piping. This excavation involves a jeopardy of flooding during the digging operation and requires a major civil engineering effort.